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From: vereijken@rulcri.leidenuniv.nl (Jan Joris Vereijken)
Newsgroups: comp.sys.ibm.pc.hardware,comp.lang.pascal
Subject: Turbo Pascal 6.0 code generation for 80286
Message-ID: <1991Mar26.010615.1@rulcri.leidenuniv.nl>
Date: 26 Mar 91 00:06:15 GMT
Sender: news@rulway.LeidenUniv.nl (Usenet news account)
Organization: Leiden University Computer Centre
Lines: 48
Nntp-Posting-Host: rulcr1

Hi,
 
I have run into something very strange: under Turbo Pascal one can choose to
generate specific 80286 code ($G+ switch). This code is not supposed to run on
XT-like (8088/8086-based) machines. However, it seems to do...
 
Facts:
 
   - My system is  V30-based clone, using a BIOS called "PC-SPEED V1.50"
     (Actually it's a modified Atari ST, it runs about every MSDOS thing
     just fine. I am sure I have a V30, as I installed it myself.)
   - I compiled (for 80286) BGIDEMO.PAS, TCALC.PAS and a few (big) things
     I wrote myself.
   - The code generated DID differ from the "normal" code (for 8088). I checked
     this. The 80286-code is shorter, and is generated faster(!).
   - All the above programs ran like a charm on my V30 machine!
   - I did NOT benchmark the speed of the 8088 vs. 80286 code. (Actually I
     did, but then proclaimed my results unreliable).
 
This is not supposed to happen! I want my machine to be locked up! I PAID for
that (Borland manuals say it should lock up).
 
I have given it some thought and have come up with the following:
 
   - Maybe a V30 (which is a enhanced 8086) can handle the 80286 instructions
     Turbo 6.0 generates? (Of course not ALL 80286 instruction, but maybe TP6.0
     only generates a proper subset.)
   - Maybe I have a BIOS that catches the 80286 instructions and emulates them?
     (Is this possible somehow? I only have a limited 8086-machinecode
     experience.)
   - Maybe the programs I ran did in fact NOT function properly, but I did not
     notice? (Say again? Me not notice???)
   - Maybe I'm going crazy? (I'm not crazy! I'm a dictionary!)
 
However, I still do not figure why things are as they are (a well-known concept
when applied to life-at-large).
 
Who sheds some light on the matter?
 
Thanx!
 
- Jan Joris -
 
forchk@rullf2.LeidenUniv.NL
vereijken@hlerul5.bitnet
 
(P.S.: Reply to me personally too, as I do not subscribe to this list.)